Conventional ion-processing apparatus is characterized by massive and complicated equipments including separately an ion chamber, an acceleration chamber, a focusing section and a workpiece mounting chamber. Since the chambers are massive, they cannot easily be evacuated. In addition, difficulties have been encountered in assuring an adequate localization of ions impinging on a desired area and a uniformity of the density of the impinging ions on a localized area. Also, the processing rate has generally been limited to an unsatisfactory level. Thus, the conventional ion-processing art has left much to be desired not only as regards equipment but also as regard to the processing precision and efficiency.